Obtaining dental images is of utmost importance for various dental and particularly orthodontic procedures in order to make treatment decisions, e.g. design braces, crowns or the like. These images also subsequently assist in monitoring the selected treatment.
Three-dimensional imaging and digitizing a teeth arrangement is a relatively complex procedure. Various methods have been proposed involving the direct imaging of teeth by probes forming part of an imaging system fixed to the skull. Such procedures, however, are difficult to practice.
There are also known several methods and systems for the so-called in-direct imaging of a teeth arrangement by acquiring images of a teeth model. Typically, in accordance with existing methods, a negative teeth model is obtained by utilizing a teeth impression in an appropriate matrix. An accurate positive model, typically a plaster model, is prepared from the negative model. The teeth model can be stored as such, photographed, scanned and stored digitally in a computer, etc.
Laurendeau, D., et al., IEEE Transactions on Medical Imaging, 10(3): 453-461, New York, USA, 1991 discloses a computer vision technique for acquiring and processing a dental image. In accordance with this technique, a standard three-dimensional teeth wax image is prepared and is optically scanned simultaneously on both sides, whereby a three-dimensional teeth image is obtained.
U.S. Pat. No. 5,237,998 discloses a three dimensional correlation of images of dental arcades, making use of an impression in the occlusive position, providing a reference in the form of three mutually spaced reference points. Three-dimensional views are taken of the impression and the points and views are also taken with the impression removed. Using the images of the reference points as a basis, the sets of views are then correlated to bring them into a single reference system.
European publication EP 634150 discloses an aid for the production of a tooth or bridge. In accordance with this technique, a model is placed on a rotary holder and during rotation is scanned by an angled scanning device.
Another technique developed by the inventors of the present invention is disclosed in WO 97/03622, which is assigned to the assignee of the present application. According to this technique, a three-dimensional representation of a teeth arrangement is obtained by providing a three-dimensional physical teeth model, removing portions of the model in a controlled, step-wise manner, and in each step, acquiring an optical image of the model or of its removed portion and digitizing each of the optical images in order to obtain a plurality of digital images. The obtained digital images are compiled to obtain a three-dimensional digital teeth representation.